The invention is based on a pressure valve as defined hereinafter. With such a pressure valve known from DE 39 04 518 A1, which is arranged in a supply line between a pump work chamber and an injection location, a valve closing element is lifted from its valve seat counter to the force of a spring by means of a medium under great pressure that is fed from the pump work chamber via the supply line to the pressure valve, causing the pressure valve to open. At the end of the high-pressure pumping, the pressure valve element returns to its seat. At the same time, an injection valve closes at the injection location, by means of which pressure waves that are in a position to re-open the injection valve run back and forth in the volume confined between the pressure valve and the injection valve. To avoid this a check valve that is guided by its closing element into the valve closing element is arranged in the interior of the valve closing element; the pressure level in the supply line can also be lowered to a static pressure that is determined by the prestressing of the restoring spring of the check valve, via this check valve, after the valve closing element has been closed.
In the known pressure valve a throttle restriction precedes to the check valve and throttles the return flow of the medium under high pressure and attenuates the rapid opening movement of the valve closing element caused by it until it contacts a filler piece, in order to reduce the mechanical load on the restoring spring. For the further return of the medium into the pump work chamber, a conduit arrangement, comprising a longitudinal bore and a transverse bore, is made in the filler piece, which, along with its stroke-limiting stop function for the check valve, also reduces the idle volume in the through bore. The options for variation of the opening pressure of the check valve and of the diameter of the upstream throttle are components of the adaptation of the total fuel injection system to the requirements of the internal combustion engine to be supplied.
If certain threshold values of peak pump pressure and the injection quantity are exceeded, the safe function of the known pressure valve is no longer assured. The throttling is no longer clearly effected at the upstream throttle; instead, the filler piece and the spring plate of the check valve work as downstream throttles, which impedes optimum adaptation of the fuel injection system to the internal combustion engine.